Apparatus for extruding ceramic slurry

ABSTRACT

An extruder includes a receptacle for containing material to be extruded. The extruder further includes a dispersion blade positioned within the receptacle and a nozzle secured to the receptacle. The nozzle defines a first opening positioned within an interior of the receptacle, defines a second opening positioned outside of the receptacle and defines a channel which extends from the first opening through the nozzle to the second opening defining a flow path which extends from the first opening, through the channel and to the second opening. The nozzle extends through a wall of the receptacle and into the interior of the receptacle such that the first opening is positioned spaced apart from the wall.

FIELD

The present application relates to additive manufacturing, and is moreparticularly directed to an extruder for extruding a heterogeneousceramic slurry.

BACKGROUND

A heterogeneous slurry, such as a ceramic slurry which containsparticles or fibers of a higher density than the liquid portion of themixture, are difficult to extrude in an additive manufacturing process.The higher density material tends to settle out of the slurry mixtureover time. With the higher density material settling out, the slurrymaterial extruded tends to lead to varying density of material beingdeposited. When the diameter of an extrusion nozzle is of the same orderof magnitude as the fibers or particles characteristic length, thefibers or particles tend to clog the nozzle and prevent the slurry fromextruding consistently or at all.

Previous attempts to resolve the problems associated with extruding aheterogeneous slurry of ceramic material included the use of higherpressure applied to the slurry to force the slurry through the nozzle.This approach however can result in inconsistent deposition andsputtering because you are expelling more liquid and leaving a higherconcentration of solid fibers behind within the nozzle.

There is a need to have an extruder which will extrude heterogeneousmixtures of ceramic slurry which contain suspended higher densitymaterial. The extruder would need to inhibit clogging of the nozzle withthe suspended material contained within the slurry mixture and wouldneed to provide an even consistent flow of well mixed heterogeneousslurry material.

SUMMARY

An example includes an extruder which includes a receptacle forcontaining material to be extruded. The extruder further includes adispersion blade positioned within the receptacle and a nozzle securedto the receptacle, wherein the nozzle defines a first opening positionedwithin an interior of the receptacle, defines a second openingpositioned outside of the receptacle and defines a channel which extendsfrom the first opening through the nozzle to the second opening defininga flow path which extends from the first opening, through the channeland to the second opening. The nozzle extends through a wall of thereceptacle and into the interior of the receptacle such that the firstopening is positioned spaced apart from the wall.

An example includes a method for extruding a heterogeneous slurrymaterial from an extruder which includes the steps of mixing theheterogeneous slurry within an interior of a receptacle of the extruderand pressurizing the heterogeneous slurry positioned within the interiorof the receptacle of the extruder. The method further includes the stepof removing the heterogeneous slurry contained within the interior ofthe receptacle through a nozzle secured to the receptacle and in fluidcommunication with the heterogeneous slurry within the interior of thereceptacle. The nozzle defines a first opening positioned within theinterior of the receptacle, defines a second opening positioned outsideof the receptacle and defines a channel which extends from the firstopening through the nozzle to the second opening defining a flow pathwhich extends through the nozzle from the first opening, through thechannel and to the second opening. The nozzle extends through a wall ofthe receptacle and into the interior of the receptacle such that thefirst opening is positioned spaced apart from the wall.

The features, functions, and advantages that have been discussed can beachieved independently in various embodiments or may be combined in yetother embodiments further details of which can be seen with reference tothe following description and drawings.

BRIEF SUMMARY OF THE DRAWINGS

FIG. 1 is a perspective view of the extruder for extruding aheterogeneous ceramic slurry of the present disclosure;

FIG. 2 is a cross section view of the extruder of FIG. 1;

FIG. 3 is an enlarged view of the extruder of FIG. 2 as identifiedwithin the circle designated as 3 within FIG. 2;

FIG. 4 is an enlarged view of the extruder of FIG. 2 as identifiedwithin the circle designated as 4 of FIG. 2; and

FIG. 5 is a flow chart of a method for extruding a heterogeneous slurrymaterial from an extruder.

DESCRIPTION

As mentioned earlier, extruding a heterogeneous material such as ceramicslurry in additive manufacturing can be problematic based on the varyingdensity of the material being extruded to be deposited. This can be thecase, for example, in additive manufacturing of low density and highporosity ceramic parts. When additive manufacturing is employed tomanufacture parts of low density and high porosity from ceramic slurry,the material needs to be extruded in the printing process from theextruder in a uniform, consistent and predictable manner. The ceramicslurry material is often in heterogeneous suspensions wherein thematerials suspended include fibers or particles that have a higherdensity than the liquid within the slurry. As a result, complicationsarise with the higher density material settling out in the extruder andblocking the outflow through a nozzle of the ceramic slurry from theextruder, such that for example a disproportionate amount of liquidflows out of the extruder compared to the amount of suspension materialssuch as fibers or particles. This can result in inconsistent deposits ofmaterial in the printing fabrication process. In some instances, thesuspension material within the ceramic slurry can completely blockoutflow of the ceramic slurry from the nozzle requiring the fabricatorto stop the process and clean the nozzle.

In referring to FIG. 1, extruder 10 includes receptacle 12 forcontaining material to be extruded from receptacle extruder 10 such as,in this example, ceramic slurry. Ceramic slurry is a heterogeneousmaterial in which an example includes an aqueous ceramic fiber slurrycontaining a body of ceramic fibers including about fifty (50) weightpercent to about eighty (80) weight percent silica fibers and abouttwenty (20) weight percent to about fifty (50) weight percent aluminafibers. Also included is xanthan gum that has a weight between about0.25 percent and about 2.5 percent of weight of the binder and the bodyof ceramic fibers before the aqueous ceramic fiber slurry is heated toprovide the slurry with a viscosity that is suitable for extrusionthrough a nozzle to manufacture a low-density, high porosity ceramicpart.

Receptacle 12 can be an unitary structure or an assembly of components.As seen in FIG. 2, in this example, receptacle 12 is constructed ofseveral assembled components which include chamber 14, top component 16and bottom wall 18. As seen in FIG. 3, top component 16 is clamped tochamber 14 with first clamp 20. Flange 22 of top component 16 and firstflange 24 of chamber 14 are secured together with first clamp 20 withfirst seal 26 positioned between flange 22 and first flange 24.Releasing first clamp 20 permits the user to remove top component 16from chamber 14 such that chamber 14 can be filled with ceramic slurryand permitting top component 16 to be reconnected and sealed to chamber14 for operation. Wall 18 of receptacle 12, as seen in FIGS. 2 and 4, issimilarly clamped to chamber 14 with second clamp 28, wherein flange 30of wall 18 and second flange 32 of chamber 14 are secured together withsecond clamp 28 with second seal 34 positioned between flange 30 andsecond flange 32. Releasing second clamp 28 permits the user to removebottom wall 18 from chamber 14 allowing nozzle 36 secured to, in thisexample, bottom wall 18 of receptacle 12 of extruder 10, to be replacedwhen needed.

Receptacle 12 includes a dispersion blade 38, as seen in FIGS. 2 and 4,positioned within the receptacle 12, which, as will be discussed in moredetail herein, is rotated within receptacle 12 mixing ceramic slurry andinhibiting suspension material such as fibers from settling out withinreceptacle 12. Mixing motor 40, as seen in FIGS. 1 and 2, includesrotatable drive shaft 42 which extends into receptacle 12 and which iscoupled within interior 50 of chamber 14 to mixing shaft 44 with shaftclamp 46. Dispersion blade 38, as seen in FIGS. 2 and 4, is secured tomixing shaft 44 such that with activation of mixing motor 40 rotation isimparted to dispersion blade 38, in this example, at a rate of rotationin a range which includes one up to and including five hundred rotationsper minute. Dispersion blade 38 is rotated mixing the higher densitysuspension material such as fibers within ceramic material withoutchopping the suspension material. The mixing maintains the higherdensity suspension material evenly dispersed within the ceramic slurryand inhibits the suspension material from settling out of the ceramicslurry.

In referring to FIGS. 2 and 3, extruder 10 further includes seal device48 positioned about rotatable drive shaft 42 and positioned betweenmixing motor 40 and a portion of interior 50 of chamber 14 of receptacle12. In this example, seal device 48 is a ferrofluidic bearing. Thissealing arrangement maintains ceramic slurry to be retained withinreceptacle 12 and permits rotatable drive shaft 42 to rotate dispersionblade 38 within interior 50 of receptacle 12 without permitting theceramic slurry to migrate along rotatable shaft 42 from out of chamber14 and top component 16 of receptacle 12, in this example.

Ceramic slurry material, in this example, is pressurized withinreceptacle 12 to provide assistance in extruding and to controlextruding the ceramic slurry through nozzle 36 for laying down theceramic slurry material. In an example of using ceramic slurry in anadditive manufacturing process wherein the ceramic material is depositedonto a cold copper surface chilled with liquid nitrogen, the rate offlow in depositing the slurry onto this chilled surface needs to becontrolled such that the material is deposited at a slow enough rate tofreeze and not puddle on the copper surface. Receptacle 12 includesinlet 52, as seen in FIG. 3, in fluid communication with interior 50 ofreceptacle 12 for introducing pressurized gas, such as air, intointerior 50 of receptacle 12. One of a wide variety of pressures can beapplied as needed to the gas including a pressure of one pound persquare inch up to including twenty pounds per square inch.

Extruder 10 further includes mechanical vibrator device 54 which issecured to or otherwise in contact with receptacle 12. Mechanicalvibrator device 54 is activated to impart vibrations to receptacle 12and to the ceramic slurry content within receptacle 12. Mechanicalvibrator device 54, in this example, includes an air powered vibratorthat imparts vibrations to receptacle 12 and to the contents such asheterogeneous slurry such as ceramic slurry. The vibrations imparted toreceptacle 12, in this example, is in the range from as low as includingfive thousand to up to and including thirty four thousand vibrations perminute. In this example, approximately ten thousand vibrations perminute are applied. The vibrations assist in maintaining the suspensionmaterial within the ceramic slurry in movement and from collecting orlumping together.

Nozzle 36, as mentioned above, is secured to receptacle 12 and in thisexample to bottom wall 18 of receptacle 12, as seen in FIGS. 2 and 4.Nozzle 36 defines first opening 56 positioned within interior 50 ofreceptacle 12, defines second opening 60 positioned outside ofreceptacle 12 and defines channel 58 which extends from first opening 56through nozzle 36 to second opening 60 defining flow path 62 whichextends from first opening 56, through channel 58 and to second opening60. Nozzle 36 extends through wall 18 of receptacle 12 and into interior50 of receptacle 12 such that first opening 56 is positioned spacedapart from wall 18. In this example, nozzle 36 includes tube 66 whichextends from wall 18 of receptacle 16 and extends within interior 50 ofreceptacle 12.

As mentioned above, first opening 56 is positioned spaced apart frombottom wall 18, as seen in FIG. 4, with extruder 10 in an operationalposition P, as seen for example in FIG. 1. When working with aheterogeneous material such as in this example ceramic slurry havinghigher density suspended material such as fibers than the density of theliquid, gravity promotes settling out of the higher density suspensionswithin the slurry and directs the suspensions toward bottom wall 18 toaccumulate such as with extruder 10 in operation position P, forexample, as shown in FIG. 1. With mixing of the ceramic slurry with theoperation of dispersion blade 38 and the agitation of the ceramic slurrywith mechanical vibrator device 54, these operations assist inmaintaining the higher density fibers in suspension and more evenlydistributed within the ceramic slurry. These techniques reduce theamount of fibers settling out of suspension during the extrudingprocess. However, the higher density suspended material such as fibersin this example that do achieve settling out through the operation ofgravity during the extruding process move toward and accumulate at aposition at or near bottom wall 18.

With first opening 56 of nozzle 36 positioned spaced apart from bottomwall 18 within interior 50 of receptacle 12, first opening 56 isbeneficially spaced apart from bottom wall 18 and the settled outmaterial such as the fibers that have settled out of suspension and haveaccumulated at bottom wall 18.

As a result, first opening 56 is beneficially positioned in the spacedapart position relative to bottom wall 18 from drawing, during theextruding process, those settled out accumulated fibers into nozzle 36and undesirably blocking even flow of the ceramic slurry through nozzle36 or otherwise blocking nozzle 36. The positioning of first opening 56spaced apart from wall 18 mitigates the occurrence of uneven depositingof the ceramic slurry and blocking of nozzle 36. As a result, a higherquality of product is manufactured and timely and costly productiondelays are avoided with respect to cleaning or replacing nozzle 36during the additive manufacturing process.

A method 100, as seen in FIG. 5, for extruding a heterogeneous slurrymaterial from extruder 10 includes step 102 of mixing the heterogeneousslurry material positioned within interior 50 of receptacle 12 ofextruder 10. Method 100 further includes step 104 of pressurizing theheterogeneous slurry positioned within interior 50 of receptacle 12 ofextruder 10.

Method 100 further includes step 106 of removing the heterogeneousslurry contained within interior 50 of receptacle 12 through nozzle 36secured to receptacle 12 and in fluid communication with heterogeneousslurry within interior 50 of receptacle 12. Nozzle 36 defines firstopening 56 positioned within interior 50 of receptacle 12, definessecond opening 60 positioned outside of receptacle 12 and defineschannel 58 which extends from first opening 56 through nozzle 36 tosecond opening 60 defining a flow path 62 which extends through nozzle36 from first opening 56, through channel 58 and to second opening 60.Nozzle 36 extends through wall 18 of receptacle 12 and into interior 50of receptacle 12 such that first opening 56 is positioned spaced apartfrom wall 18.

Step 104 of pressurizing heterogeneous slurry further includes a step ofinserting pressurized gas through inlet 52 of the receptacle 12 intointerior 50 of receptacle 12 containing the heterogeneous slurry. Step104 of pressurizing the heterogeneous slurry also includes the step ofpressurizing the pressurized gas in a pressure range of including onepound per square inch up to and including twenty pounds per square inch.

Step 102 of mixing further includes a step of activating motor 40,including rotatable drive shaft 42 which extends from motor 40 intoreceptacle 12. Step 102 of mixing further includes coupling rotatabledrive shaft 42 to mixing shaft 44 with mixing shaft 44 secured todispersion blade 38 such that with activating of motor 40 dispersionblade 38 rotates within interior 50 of receptacle 12.

Step 104 of pressurizing the heterogeneous slurry further includescontaining the pressurized heterogeneous slurry within receptacle 12along rotatable drive shaft 42 with seal device or ferrofluidic bearing48, as seen in FIG. 3, positioned around rotatable drive shaft 42. Step102 of mixing further includes rotating rotatable drive shaft 42 in arange which includes one up to five hundred rotations per minute.

Method 100 for extruding a heterogeneous slurry material from extruder10 further includes a step of activating a mechanical vibrator device 54associated with chamber 14 of receptacle 12 imparting vibrations tochamber 14 and the heterogeneous slurry positioned within interior 50 ofthe chamber 14 of receptacle 12.

Method 100 for extruding a heterogeneous slurry material from extruder10 further includes a step of placing heterogeneous slurry, whichcomprises ceramic slurry which comprises a plurality of fibers, intochamber 14 of receptacle 12.

Step 106 of removing of the heterogeneous material is conducted at aselect flow rate including a flow rate which includes two up to andincluding fifty grams per second.

While various embodiments have been described above, this disclosure isnot intended to be limited thereto. Variations can be made to thedisclosed embodiments that are still within the scope of the appendedclaims.

What is claimed:
 1. An extruder comprises: a receptacle for containingmaterial to be extruded; a dispersion blade positioned within thereceptacle; and a nozzle secured to the receptacle, wherein: the nozzledefines a first opening positioned within an interior of the receptacle,defines a second opening positioned outside of the receptacle anddefines a channel which extends from the first opening through thenozzle to the second opening defining a flow path which extends from thefirst opening, through the channel and to the second opening; and thenozzle extends through a wall of the receptacle and into the interior ofthe receptacle such that the first opening is positioned spaced apartfrom the wall.
 2. The extruder of claim 1, further includes a mixingmotor which comprises a rotatable drive shaft which extends into thereceptacle.
 3. The extruder of claim 2, further includes a shaft clampcoupling the rotatable drive shaft to a mixing shaft.
 4. The extruder ofclaim 3, wherein the dispersion blade is secured to the mixing shaft. 5.The extruder of claim 2, further includes a seal device positioned aboutthe rotatable drive shaft.
 6. The extruder of claim 5, the seal deviceis positioned between the mixing motor and the interior of thereceptacle.
 7. The extruder of claim 5, wherein the seal devicecomprises a ferrofluidic bearing.
 8. The extruder of claim 1, whereinthe receptacle further comprises an inlet in fluid communication withthe interior of the receptacle for introducing pressurized gas into theinterior of the receptacle.
 9. The extruder of claim 1, further includesa mechanical vibrator device associated with the receptacle.
 10. Theextruder of claim 1, wherein the nozzle comprises a tube which extendsfrom the wall of the receptacle and within the interior of thereceptacle.
 11. A method for extruding a heterogeneous slurry materialfrom an extruder, comprising the steps of: mixing the heterogeneousslurry within an interior of a receptacle of the extruder; pressurizingthe heterogeneous slurry positioned within the interior of thereceptacle of the extruder; and removing the heterogeneous slurrycontained within the interior of the receptacle through a nozzle securedto the receptacle and in fluid communication with the heterogeneousslurry within the interior of the receptacle, wherein the nozzle definesa first opening positioned within the interior of the receptacle,defines a second opening positioned outside of the receptacle anddefines a channel which extends from the first opening through thenozzle to the second opening defining a flow path which extends throughthe nozzle from the first opening, through the channel and to the secondopening; and the nozzle extends through a wall of the receptacle andinto the interior of the receptacle such that the first opening ispositioned spaced apart from the wall.
 12. The method of claim 11, thestep of pressurizing the heterogeneous slurry further includes insertingpressurized gas through an inlet of the receptacle into the interior ofthe receptacle containing the heterogeneous slurry.
 13. The method ofclaim 12, the step of pressurizing the heterogeneous slurry includes thestep of pressurizing the pressurized gas in a pressure range ofincluding one pound per square inch up to and including twenty poundsper square inch.
 14. The method of claim 11, the step of mixing furtherincludes the step of activating a motor, comprising a rotatable driveshaft which extends from the motor into the receptacle.
 15. The methodof claim 14, the step of mixing further includes coupling rotatabledrive shaft to a mixing shaft with mixing shaft secured to a dispersionblade such that with the activating of the motor the dispersion bladerotates within the interior of the receptacle.
 16. The method of claim14, the step of pressurizing the heterogeneous slurry further includescontaining the pressurized heterogeneous slurry within the receptaclealong the rotatable drive shaft with a ferrofluidic bearing positionedaround the rotatable drive shaft.
 17. The method of claim 15, the stepof mixing further includes rotating the rotatable drive shaft in a rangewhich includes one up to five hundred rotations per minute.
 18. Themethod of claim 11, further includes activating a mechanical vibratordevice associated with a chamber of the receptacle imparting vibrationsto the chamber of the receptacle and the heterogeneous slurry positionedwithin the interior of the chamber of the receptacle.
 19. The method ofclaim 11, further includes the step of placing the heterogeneous slurry,which comprises a ceramic slurry which comprises a plurality of fiber,into the chamber of the receptacle.
 20. The method of claim 11, the stepof removing includes removing the heterogeneous material at a flow ratein a range of which includes two up to and including fifty grams persecond.